Hi ive got a Peavey XR684 in for repair and the main amp works but the pre amp dosnt.All surface mount components.Any help would be great cheers andy
Hello, I have a couple of questions before I can help you.- when you say the preamp doesn't work, are you getting no audio input and output from any jacks, or is there a more specific issue? If there is a specific issue please state what it is. - do you have a schematic for this amplifier?- what checks have you made so far? Have you checked power supply voltages?
Hi yeah no signal from input to output.The graphic leds are all on on the oneside.Checked all voltages and there fine.Ive injected a signal and after replacing a couple of ics on the channels im getting a very small signal.Ive got a schematic ,ill try and upload it to u.cheers
have u a email address to send it to
Hi yeah no signal from input to output.The graphic leds are all on on the oneside.Checked all voltages and there fine.Ive injected a signal and after replacing a couple of ics on the channels im getting a very small signal.Ive got a schematic ,ill try and upload it to u.cheers XXXX X a email address to send it to ,
I have the schematic. I just wanted to make sure you did also, as it would be difficult to troubleshoot without it. Did you check the Monitor and Tape Outs also?You say that the graphic LEDs are all on with no sound. That is a sign that they are seeing DC voltage, which usually indicates that one of the bipolar supplies is down, or an op-amp is bad. Did you check the voltages right at the op-amps, or just at the supply. You may be losing a voltage somewhere in between. I would suggest putting in a signal and tracing through the circuit with an oscilloscope to see where you do and don't have signal. Check the voltages right at the op amps that are not passing signal, and check for DC voltage on the audio lines. A bad op amp will often put out DC, which will swamp out the audio. In this case I think you are losing the + or -15 volts somewhere in the circuit. But the results of some signal tracing will tell us much more.